In the use of numerically controlled or programmable robots, it is desirable to protect the robot and the tooling carried by the robot arm in addition to any article carried by the tooling in the event the article or tooling inadvertently or accidentally hits an object while the robot arm is in motion. Usually, such protection is provided by a coupling or link member which connects the robot arm to the tooling and is adapted to break or slip if the tooling or article carried by the tooling receives an impact or force. When a link member breaks, the tooling usually drops to the limit of a retaining chain or cable. A maintenance man or operator must then replace the link member and repair any damage to the robot and/or tooling before the robot may be placed back in operation. Usually, such replacement and/or repair requires substantial time, and this results in production down time for not only the robot but other associated equipment which the robot is serving.
One form of safety device or mechanism is disclosed in International Patent Application No. PCT/JP81/00377 published by the Japanese Patent Office on June 24, 1982. The mechanism disclosed in this patent application forms a coupling between the robot arm and the fixture or tooling supported by the arm and includes a weight element supported by a set of tension springs. Movement of the weight element in response to a lateral impact or force on the fixture or tooling results in actuating a switch which stops the movement of the robot arm. However, if the tooling or article carried by the tooling inadvertently hits a stationary object or an object having substantial mass, the robot arm or tooling or article may be damaged before the robot arm stops. If the tooling or robot arm is bent, substantial down time may be required to repair the arm or tooling and also realign the tooling with respect to the robot arm.